With rapid development of science and technology and internet technology, some network resources are applied more frequently, personal information is increasingly input on the network, and leakage of the personal information has always been a problem to be solved. Biometric identification technology has attracted more and more attentions in recent years since a fingerprint has uniqueness and stability. A conventional method for fingerprint identification is as shown in FIG. 1, which includes fingerprint preprocessing, fingerprint minutia extracting, fingerprint registration and matching; where when a fingerprint minutia is extracted, in order to add information of the minutia, besides that a position and a direction of the minutia are recorded, three parameters which represent directions of three vertexes of a regular triangle taking the minutia as a center and a fixed value as a circumradius are added, so that a conventional expression structure of the minutia is [(x y) θa θb θc], where θa, θb, θc represent the directions of the three vertexes around the minutia respectively. However, a fingerprint is easy to distort and stability and specificity of the above-mentioned conventional expression of the minutia are not better enough, which causes that subsequent registration and matching are not accurate.